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How to deactivate SDM and allow for screw drive autofocus with DA* 50-135mm f/2.8

mercredi 2 janvier 2013, par Clover


ATTENTION PLEASE : THIS IS UNOFFICAL INSTRUCTIONS, FOLLOW THEM AT YOUR ONWN RISK.

This article is born after a long and interesting thread on pentaxkpark.com
Thanks again, to poildegris for his help and also to nicokoscom55 for his work, I am only the messenger.

Let’s start.

Few Pentax lenses have the ability to do autofocus with SDM or with the motor inside the body if the body does not allow SDM.

These SDM * lenses are :
- smc PENTAX-DA* 16-50mmF2.8 ED AL [IF] SDM
- smc PENTAX-DA* 50-135mm F2.8 ED [IF]SDM
- smc PENTAX DA* 60-250mm F4ED [IF] SDM
- smc PENTAX-DA* 200mmF2.8 ED[IF] SDM
- smc PENTAX-DA* 300mmF4 ED[IF] SDM

The process begins likely as updating the firmware, with press and holding MENU button, but we will not use a firmware but a Text document created as written in Pentax-hack.info website.

Each command will need a different SD card or to rewrite the MODSET file.

Main steps are
- 1 Using a file to access the debug mode
- 2 Using a file to show the list of commands and then save the original EEPROM
- 3 Changing the EEPROM file with notepad++ or the Body it self
- 4 Load the modified EEPROM inside the lens
- 5 deseactivating the debug mode

The easiest is to use a Pentax K-7 with PKTETHER.

As I do not own all SDM DA* lenses, I will only talk about the process using a 50-135mm DA* with my K-7.
Let’s start after the battery fully charged and the 50-135mm mounted on it.

STEP 1
Here is the process using a Pentax K-7

Download PKTETHER
http://www.pktether.com/

Plug your K-7 to your computer using the USB cable ( sold with the body) and launch PKTETHER
Switch ON the DEBUG MODE by click on CAMERA DEBUG MODE ON

STEP 2
Take back your SD card and, using Notepad, create a file nammed MODSET.474
inside, only write (after un blank line) :

[OPEN_DEBUG_MENU]

Put the file in the root of the SD cardPut the card inside the switched Off DSLR.
Press and Hold MENU button and switch on the DSLR.

If everything OK, it will show you all options avaible on Debug mode :
Beware to not change a thing you do not need ( once again, all this are made at your own risk)

Use the pad to go to the line
LENS ROM CAMERA=>SD

Make a saved file of the EEPROM to allow you to reverse the process in cas of troubles ( save i_t in a different file if youi also do the same for an other sdm Lens)

STEP 3
To modify the EEPROM, you can
- Either access the LENSEEP.LNS file you create by saving the file, I ask you to use Notepad++
- Or go to the line :
LENS EEPROM READ/WRITE
You can change the code line by line

Using NOTEPAD++ : DO NOT FORGET TO SAVE A FILE AND MODIFY A COPY FOR YOUR OWN SECURITY

Then change the code "C0" by "80" in the colonn 03,for the following lines

  • 0020
  • 0060
  • 00A0
  • 00E0
  • 0120
  • 0160
  • 01A0
  • 01E0
  • 0220
  • 0260
  • 02A0
  • 02E0
  • 0320
  • 0360
  • 03A0
  • 03E0
  • 0420
  • 0460
  • 04A0
  • 04E0
  • 0520
  • 0560
  • 05A0
  • 05E0
  • 0620
  • 0660
  • 06A0
  • 06E0
  • 0720
  • 0760
  • 07A0
  • 07E0 Using the DSLR directly : DO NOT FORGET TO SAVE A FILE AND MODIFY A COPY FOR YOUR OWN SECURITY Access the line LENS ROM EDIT R/W using the pad and the OK button. Using the pad and dial, access the READ /WRITE function, check by read the info before modify it. Really check the info at the adress before change it. You need to read "C0" WRITE "80"
  • 0023
  • 0063
  • 00A3
  • 00E3
  • 0123
  • 0163
  • 01A3
  • 01E3
  • 0223
  • 0263
  • 02A3
  • 02E3
  • 0323
  • 0363
  • 03A3
  • 03E3
  • 0423
  • 0463
  • 04A3
  • 04E3
  • 0523
  • 0563
  • 05A3
  • 05E3
  • 0623
  • 0663
  • 06A3
  • 06E3
  • 0723
  • 0763
  • 07A3
  • 07E3

STEP 4
Put the modified fil LENSEEP.LNS in the root of the card and load it as using the Debug mod ( line under the line you use for saving the file )

LENS ROM DAT SD => CAMERA

STEP 5
Check your lens on the DSLR, the SDM will no more work.

Then Plug your K-7 to your computer and launch PKTETHER
Switch off the DEBUG MODE by click on CAMERA DEBUG MODE OFF

Tadaaaaaa !

If everything OK, you did it, the DSLR will work as before, and the 50-135mm will not use SDM on any DSLR unlast you relaod the old LENSEEP.LNS.

2 Messages

  • Hi Clover,

    This is great article, thank you for sharing. I have a Pentax DA* 60-250mm lens and a Pentax K-30 camera. The SDM motor has stopped working. Can I use the same instructions to convert to screw driven for my lens ?

    Thank you !

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  • Incredible ! It works ! After 2 years of being a vegetable my DA*50-135 is focussing again.
    The pkteather program didn´t work for me, it wasn´t able to put the camera to debug mode.
    Editing the adresses in the camera didn´t work either because the in-body "browser" or whatever you want to call it wouldn´t go to adresses above 03E*.
    So I exported a LENSEEP.LNS to a SD card, edited the file in Notepad++, and loaded it from an SD card to the camera again.
    And by the way, the only way to produce a functional debug mode was by loading a MODSET.474 file containing
    "
    [DEBUG_MODE EN]
    [OPEN_DEBUG_MENU]
    [SW_DEBUG_MENU EN]"
    to an SD card and switching the camer on while holding menu.
    It took about 7 attempts but in the end it worked.
    Wow, thanks all you guys who contributed.

    Best regards, Vigfus

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